Retractable cryogenic assembly



March 12, 1968 M. `WALDMAN 3,372,556

l RETRACTABLE CRYOGENIC ASSEMBLY Fild March 25, 1966 @Alia2 I cana/any55 SSE/77 y 30 ,Q6

United States Patent l 3,372,556 RETRACTABLE CRYOGENIC ASSEMBLY MarvinWaldman, Ontario, Calif., assigner to General Dynamics Corporation, acorporation of Delaware Filed Mar. 25, 1966, Ser. No. 537,535 9 Claims.(Cl. 62.-45)

ABSTRACT OF THE DESCLOSURE Broadly, the disclosure relates to aninfrared tracking or seeking head provided with a cryostat coolingmeans, this being such that the cryostat is detachable from the seekerhead so as to permit the detector section to be gimbaled. The cryostatunit extends into the detector cooling chamber through an O-ring sealand is provided with a solenoid control unit which operates to withdrawthe cryostat from the cooling chamber. The chamber is provided with aninternal spring loaded door which seals the chamber when the cryostat isremoved.

This invention relates to refrigeration devices, particularly torefrigeration devices for cooling radiation sensing devices, and moreparticularly to detachable refrigeration devices for gimbaled radiationdetection devices.

Much effort has 4been directed to the development of refrigerationdevices, particularly those utilizing the Joule- Thomson effect. Withthe advent of missiles and space vehicles, the need for effectiverefrigeration devices or heat exchangers has greatly increased.

As is well known, many of the present day missiles and space vehicles,as well as land based equipment, utilize energy-detecting units such asthose used for detecting infrared or heat radiation.

Infrared detectors, for example, are being used for a variety ofpurposes especially by the military forces, and to provide a detector ofrequisite sensitivity, namely, one having optimum spectral response andcapable of detecting small temperature differences, requiring that thedetector cell be maintained at cryogenic temperatures. One common methodof accomplishing this low temperature is by expanding a pressurizedrefrigerant in the vicinity of the cell and returning the cool expandedrefrigerant in regenerative heat exchange with the incoming refrigerantto cool the refrigerant before or during expansion and thereby to attaina greater Joule-Thomson effect.

Low temperature regulators of this type, often referred to as cryostats,have the advantage of being free of moving parts which are susceptibleto low temperature malfunctioning, in addition to being of extremestructural compactness. While cryostats operating on the expansion orJoule-Thomson cooling principle exist in a multitude of forms, theytypically comprise a tightly wound coil of high-heat-conductivity tubinghoused in an insulating sheath and adapted to transport gaseous mediaunder high pressure to an expansion orifice or throttling yvalve,through which the gas is expanded to approximately atmospheric pressure.The Joule-Thomson cooling resulting from expansion causes a lowering oftemperature, and the cooled expanded gas is constrained to pass backover the incoming passages of the cryostat or heat exchanger, to coolthe incoming high-pressure stream.

The application of infrared to airborne -lire control system is beingrapidly expanded, and infrared detectors are now being designed toreplace the radar gear in certain air vehicles. Infrared equipment isfinding increased use as it has many advantages over other types of firecontrol equipment. Infrared equipment is inherently more accurate thanradar as it has greater resolution and no side lobes to give groundreturn or sea clutter. However,

3,372,555 Patented Mar. l2, 1968 the most important advantage ofinfrared equipment is the passive nature of the equipment and thedifficulty of successful enemy countermeasures. No energy is emitted bythe fire control system which can -be used by an enemy for eitherdetection or jamming.

As pointed out above, the infrared detection cell is most effective whenmaintained at an extremely low ternperature, such as the temperature ofliquid nitrogen. Normally, the detection cell is mounted in a fixedposition when mounted in a hunting device, such as the seeker head of amissile which moves up, down, and sideways in order to cover thegreatest possible searching area. With such fixed position detectioncells, it is readily easy to provide a cryogenic device for cooling thecell. However, it has been found desirable to gimbal the detection unitto provide a better scanning-tracking detector systern. With a gimbaleddetection unit, the prior known cooling methods are unsatisfactory inthat they have been fixed with respect to the cell. Therefore, a needhas been developed for a means of cooling a gimbaled detector unit.

The present invention provides a means of cooling a gimbaled detectorunit, whereby a more ecient scanningtracking detector system can beutilized. This is accomplished by providing a means for retractablypositioning the cryostat such that it is withdrawn after the detectorcell has been cooled, thus allowing the detector to be readily gimbaled.

Therefore, it is an object of this invention to provide a cryogenicassembly for cooling radiation-sensitive detectors.

Another object of the invention is to provide a retractably mountedcryogenic apparatus.

Another object of the invention is to provide a detachable cryostat forinfrared detection units.

Another object of the invention is to provide a retractable cryostat forinfrared sensitive scanning-tracking systems whereby the detector unitthereof may be gimbaled.

Other objects of the invention will become readily apparent from thefollowing description and accompanying drawings wherein:

FIG. 1 is a perspective view of an air vehicle capable of utilizing theinvention;

FIG. 2 is a view partially in cross section of a prior art seeker headillustrating the fixed type detector cell; and

FIG. 3 is a diagrammatic view illustrating the invention.

Referring now to the drawings, FIG. l shows, for purposes ofillustration, a missile 10 including an infraredtracking seeker section11; a guidance and control section 12 including electronic processingcircuitry and two fixed and two movable, single-plane,variable-incidence folding control surfaces 13 and 14, respectively,only one movable control surface 14 being shown; a warhead/fuze section15; a dual stage rocket motor section 16; and a tail section 17 havingfour folding nonvariable tail surfaces 18.

The intelligence necessary for missile guidance is developed in theinfrared-sensing seeker section 11, whose primary functions are to trackheat radiated from the target and to provide a signal proportional tothe rate of change of the angular line-of-sight to the target. Seekerintellegince is converted into airframe corrective maneuvers by theguidance and control section 12 to maintain the missile on a collisioncourse. Since the operation of the control section 12 is not part ofthis invention, a detailed description thereof is not deemed necessary,but the control section may be of the type described in the U.S. patentapplication Ser. No. 397,674, and assigned to the assignee of thepresent application.

FIG. 2 shows portions of a prior art seeker head 19 of the seekersection 11 illustrating the fixed type detector cell and the associatedcryostatic cooling mechanism. Generally, the seeker head 19 includes asupport member 20 adapted to be attached to the missile 10, a support orgimbal post `21 operatively attached to support member 20, a gimbal 22operatively mounted 'via bearings 23 and 24. within post 21, and adetector 25 gas cooled by a cryostat 26 which is supplied with highpressure coolant via intake line 27, the coolant being dischargedthrough exhaust line 28 in conventional manner. Operatively connected togimbal 22 is a bearing mount 29 within which is positioned a reticleassembly 30 and spin bearings 31. An optical barrel 32 is connected viabearings 31 with bearing mount 29 and gimbal 22. Barrel 32 supports amagnet 33, primary mirror 34, and secondary mirror 35 having sunshade 36thereon.

As can be readily seen, the optical barrel 32 is gimbaled so that it maymove with respect to the post 21 while spinning on bearings 29 in amanner known in the art. With the FIG. 2 arrangement, the detector 25 isfixed with respect to post 21 and thus does not move with the opticalbarrel 32 and the associated optics thereon.

Referring now to FIG. 3 which diagrammatically shows the inventiveconcept of providing a retractable or detachable cryostat which allowsthe detector to be gimbaled with the associated optics. Generally, theinvention, as illustrated, comprises a housing 40 within -which ismounted at window 41, a detector support structure 42 and a chambersealing door 43. Detector support structure is provided with a filter 44on the forward side and a detector unit 45 on the opposite or rearwardside thereof, and is spaced in chamber 46 by spacers 47 and 4.8, supportstructure 42 and window 41 defining an evacuated area 49 therebetween.Chamber sealing door 43 is movably mounted on pins 50 which are xedlyattached to wall 51 of housing 40. Door 43 is adapted to be closedagainst housing wall 51 by resilient means such as springs 52operatively mounted on pins 50. Housing wall 51 is provided with anaperture 53 through which a cryostat 54 enters to cool detector 45 andchamber 46. The cryostat 54 includes a supply line 55 and an exhaustline 56, and may be of the type illustrated in FIG. 2 or any othersuitable configuration. Cryostat 54 is mounted within a cryostat housing57 which is abutted on housing 40 via a sealing washer 58. An O-ring 59is mounted in aperture -v 53 of housing 40 surrounds the inner end ofcryostat 54 and prevents leakage of coolant therearound. Operativelyconnected to cryostat housing 57 is a housing`60 within which ispositioned a solenoid indicated by legend 61 which, while not shown, isoperatively connected with cryostat 54.. A spring 62 surrounds cryostat54 and functions along with solenoid 61 to move the cryostat withinaperture 53 of housing wall 51.

In the normal process of firing the FIG. 1 missile, for example, thegyro of seeker head, which would be attached to the optics and detectorunit 45, starts to spin up by an appropriate power source, and thedetector is cooled by high pressure coolant being supplied via line 55,expanded into chamber 46, and exhausted via line 56. The force of thepressurized coolant causes door 43 to move slightly away from cryostat54. After the cooling cycle has been completed and the gyro is stillcaged, the cryostat 54 is retracted by the solenoid 51 which overcomesthe tension of spring 62 which normally holds the cryostat in theposition shown in FIG. 3. As the cryostat 54 is retracted from withinchamber 46 the aperture 53 in housing wall 51 is automatically sealed bythe door 43 due to the expanding of springs S2 leaving the expandedcoolant in contact with detector 45. The gyro is then uncaged and themissile 10 fired. Retracting of the cryostat 54 from within housing 4,0allows the detector 4S to be gimbaled along with the optical barrel 32(see FIG. 2).

The advantages of the present invention are: (1) shorter cooling-downtime; (2) lower temperatures in cooling 4 chamber; (3) less area tocool; and (4) coolant in contact with the detector for a longer periodof time.

It has thus been shown that the present invention provides a systemwherein a cryogenic apparatus cools the radiation detector unit,withdraws itself, and seals the detector containing chamber, whereby thedetector can be readily gimbaled with other associated equipment such asthose elements of a seeker head of a homing type missile. Thus, withthis invention a more effective scanning-tracking radiation detectorsystem serves to advance the state of the art.

Although a specific embodiment has been shown for purposes ofillustration, modifications and changes will become apparent to thoseskilled in the art, and it is intended to cover in the appended claimsall such modifications and changes as come within the true spirit andscope of the invention.

What I claim is:

1. In a radiation sensitive scanning-tracking device, a retractablecryogenic apparatus comprising: a housing defining la chamber, saidhousing being provided with an aperture, movable means operativelyconnected to said housing for sealing said aperture, a cryostatoperatively associated with said housing and adapted to extend throughsaid aperture and adapted to at least partially move said sealing means,and means for extending said cryostat to within said chamber andretracting same from therein, whereby coolant under pressure is suppliedby said cryostat to said chamber for cooling same and whereafter saidcryostat is retracted from within said chamber and said sealing meansseals said aperture.

2. The apparatus defined in claim 1, wherein said housing contains aradiation sensitive means.

3. The apparatus defined in claim 2, wherein said radiation sensitivemeans comprises an infrared sensitive detector unit.

4. The apparatus defined in claim 1, wherein said aperture sealing meansincludes a door-like member slidably mounted on pin-like means fixedlyattached to said housing, and resilient means operatively mounted withrespect to said pin-like means and said door-like means so as to movesaid door-like means against said housing aperture to seal said housingchamber.

5. The apparatus defined in claim 1, wherein said housing aperture isprovided with a sealing member, said sealing member extending aroundsaid cryostat, thereby preventing leakage of coolant therebetween whensaid cryostat is extended into said chamber.

6. The apparatus defined in claim 1, wherein said cryostat moving meansincludes a solenoid and a spring member, said spring member normallyfunctioning to maintain said cryostat extending into said chamber, saidsolenoid functioning to retract said cryostat from within said chamber.

7. The apparatus defined in claim 1, in combination with a seeker head,said seeker head including an optical assembly for directing a signal toa radiation sensitive means mounted within said seeker head, and meansfor movably supporting at least said optical assembly.

8. The combination defined in claim 7, in combination with an airvehicle, said seeker head being mounted in said vehicle and adapted forguiding same via a plurality of control surfaces operatively mounted onsaid vehicle.

9. The combination defined in claim 7, wherein said radiation sensitivemeans comprises an infrared sensitive detector unit.

References Cited UNITED STATES PATENTS LLOYD L. KING, Primary Examiner.

